Greenhouses are intended to protect crops from hail, rain, wind, and sun and control the effect of various environmental conditions. Current greenhouse films are mainly fabricated with Polyethylene (PE) and for the high-demand market they may also contain Ethylene Vinyl Acetate (EVA). A typical greenhouse film formulation may contain: 0-20% of EVA with 4 to 19% VA content, 20-30% of Linear Low Density Polyethylene (LLDPE), and 50-70% of Low Density Polyethylene (LDPE).
EVA is an ethylene vinyl acetate copolymer intended to impart beneficial thermal properties to the film. It is also believed that EVA restricts the migration of thermal additives onto the film surface thereby reducing loss of the thermal additive. Maintenance of the thermal additives over the life of a greenhouse film ensures maintenance the greenhouse effect inside the structure favoring the growth of the crops. Other properties provided by the EVA are the elasticity and creep resistance which are critical to facilitate the installation of these films and also to prevent or minimize sagging during normal use. The price of EVA depends on the vinyl acetate content, which typically may vary from 4 to 19%. Further, EVA is not always readily available in the market, further impacting its cost.
An alternative to EVA content in greenhouse films would be desirable to counteract the cost impact of EVA provided such alternative provides good thermal and mechanical properties.